Clinicopathological analysis of PD-L1 and PD-L2 expression in pulmonary squamous cell carcinoma: Comparison with tumor-infiltrating T cells and the status of oncogenic drivers.

Abstract Purpose Programmed cell death-1 (PD-1)/programmed cell death-ligand-1 (PD-L1) pathway-targeted immunotherapy has beneficial therapeutic effects in pulmonary squamous cell carcinoma (SqCC) patients. However, the expression patterns of PD-1 and PD-1 ligands (PD-Ls) in pulmonary SqCC remain unclear. Moreover, the association between the PD-1/PD-Ls pathway and the status of oncogenic drivers in pulmonary SqCC is unknown. Methods PD-L1 and PD-L2 expression in tumor cells and the numbers of PD-1 + and CD8 + tumor-infiltrating lymphocytes (TILs) were examined in 331 resected SqCC tumors along with matched lymph node metastases from 77 cases using immunohistochemistry. EGFR and FGFR1 and MET expression and genetic status were also examined. Results PD-L1 and PD-L2 expression was detected in 26.9% and 23.9% of the pulmonary SqCC samples, respectively. PD-L1 and PD-L2 expression was maintained or increased in the metastatic lymph node tumors in 81.1% and 93.5% of the 77 cases, respectively. The numbers of PD-1 + and CD8 + TILs were significantly positively correlated ( P + T cell infiltration ( P + TILs ( P =0.001 for both). Increased numbers of CD8 + or PD-1 + TILs were significantly associated with prolonged disease-free survival of these patients, whereas PD-L1 and PD-L2 expression had no significant prognostic implications. Conclusion PD-L1 and PD-L2 expression in pulmonary SqCC is associated with an increased number of CD8 + TILs and increased MET expression, which might provide therapeutic insight into targeting the PD-1/PD-Ls pathway in pulmonary SqCC.